Elizabeth,
Over the past 10 years I have purchased 3 Dell computers and have been happy with them all (all are still running). 512 memory is the minimum requirement, but should be OK. My concern would be the graphics and whether or not the 512 memory is "shared" or not. Dell has several models with "shared memory", which shares as much as 224mb to support graphics. I think this could affect performance greatly. A system with a min. 64mb graphics card would be my recommendation-and no "shared" memory. Looking at Dell's August catalog, the Dimension 5100 would be my choice as a minimal system configuration. Just my opinion, though.
Steve
AC19(9001), 27" iMac i7, 12 gb ram, ATI Radeon HD 4850 512mb, OS 10.12.6